Nitride and polysilicon interface with titanium layer

Abstract

A conductive structure in an integrated circuit (12), and a method of forming the structure, is provided that includes a polysilicon layer (30), a thin layer containing titanium over the polysilicon, a tungsten nitride layer (34) over the titanium-containing layer and a tungsten layer over the tungsten nitride layer. The structure also includes a silicon nitride interfacial region (38) between the polysilicon layer and the titanium-containing layer. The structure withstands high-temperature processing without substantial formation of metal silicides in the polysilicon layer (30) and the tungsten layer (32), and provides low interface resistance between the tungsten layer and the polysilicon layer.

Description

[0001] This application is a continuation of co-pending International Application No. PCT / US2003 / 029085, filed Sep. 16, 2003, which designated the United States and was published in English, and which claims priority to U.S. Provisional Patent Application No. 60 / 411,710, filed Sep. 18, 2002, both of which applications are incorporated herein by reference.TECHNICAL FIELD [0002] The present invention relates to conductive structures used in semiconductor devices and to methods of manufacturing the same. BACKGROUND [0003] Polycrystalline silicon or “polysilicon” structures are commonly used as conductive elements in integrated circuits. [0004] For example, in memories and other devices, an oxide-insulating layer overlies the channel region of a field effect transistor (“FET”) and a conductive polysilicon layer overlying the oxide layer serves as the gate of the FET. The amount of electrical charge on the gate controls the conductivity through the channel region of the FET. Thus, the sp...

AI Technical Summary

Benefits of technology

[0018] Desirably, the metal nitride layer is about 1-24 nm (10-240 Å) thick and preferably about 4 nm to about 16 nm thick, and most desirably about 4 nm to about 10 nm thick, although thicker nitride layers can be used. The relatively thick nitride layer tends to provide a fine grained structure at the surface remote from the interface metal layer and the silicon-containing layer, which, in turn, favors the growth of relatively large grains in the conductor metal. This, in turn, enhances conductivity of the conductor metal and, hence, conductivity of the entire structure.

Problems solved by technology

The layer including the interface metal, as deposited, desirably is relatively poor in nitrogen.

However, the structure, after high temperature processing, has an interface resistance substantially lower than a comparable structure with a metal nitride layer but without the interface metal.

It is believed that this, in turn, leads to a lower interface resistance than would occur in the absence of the interface metal.

However, it is also believed that the interface metal does not form a complete barrier to diffusion of nitrogen into the polysilicon layer, and that some silicon-nitrogen compounds form in the interfacial region of the polysilicon layer and serve as a barrier to diffusion of metal into the silicon-containing layer or diffusion of silicon into the metal layer.

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